The usage of alternative translation initiation sites have been discussed for disease-causing proteins such as parkin, the prion protein and the breast cancer antigen BRCA1. Here,Dinaciclib we provided evidence that the second in-frame ATG codon in the TPI gene encoding MET14 can be used as an alternative translation initiation site in yeast as well as in mammalian cells. However, the resulting protein did not suppress the growth defect of Dtpi1 yeast on glucose medium indicating that this variant lacks catalytic activity. This result is not unexpected, since this TPI variant lacks the catalytic lysine and at least three residues of the intersubunit interface. Interestingly, a TPI deficiency patient which has inherited a start codon mutation in combination with the mutation at posi-tion 104, has a stronger pathology in comparison to Glu104Asp homozygotes. Structural alterations of the pathogenic TPI variants have often been speculated to contribute to TPI deficiency as a number of mutations seem to affect the dimerization interface of TPI which forms a stable dimer in most investigated organisms. To address this issue,BAY 43-9006 we have analyzed the dimerization properties between wild-type and the pathogenic TPI variants by a quanti-tative assay that is based on the lacZ gene as reporter. This allows determination of the relative strength of protein-protein interac-tions in yeast, however, these values can not be directly correlated with binding constants determined by in vitro measure-ments. We discovered that the dimerization behavior between wild-type TPI and the two pathogenic variants Cys41Tyr and Glu104Asp is strongly altered compared to the dimerization behavior between wild-type proteins. We further observed that the glycolytically inactive TPI2ndATG variant dimerizes with wild-type TPI, although at reduced levels in comparison to the dimerization of wild-type TPI proteins. Finally, we demonstrated that the dimerization between the pathogenic variants also occurred with lower stringency as indicated by the relative activity of the lacZ reporter gene.